An excavator encounters a reaction force of 7600 lb from the ground, normal to line AC, as shown. The shaded structural members (Dipperstick (FH), Mainboom (ADK), bucket, and hydraulic cylinders) have a combined weight of 15000 lb and a horizontal mass center located midway between points C and G.

Derive the equation of motion for the following system, using (the rotation of the beam about the hinge) as the degree-of-freedom. Not that there is an applied force (Fo sin wt) as well as an applied moment (Mo sin wt). The total bar mass is m. Treat the bar as two bars: one to the left of the hinge point; one to the right. The one to the left has a mass moment of inertia of- mL²; the one to the 27 192 1 mL². Then transform this Fo sin cor right has a mass moment of inertia of- 192 differential equation of the Laplace domain, assuming zero initial conditions. Lastly, compute the damping ratio and damped natural frequency for this system. TET 4 fm o Mo sin or

Problem 4. A thin, semi-circular ring of mass m and radius R is pinned to ground at point O. The bar is released from rest in the position shown. Note that a = 2R, IG = mR² - ma² (a) Find the mass moment of inertia of the body about point O (b) Find the angular acceleration of the ring when released (c) Find the reaction forces on the ring at point O Ans: (b) a=0.5(g/R); (c) Ox = (mga)/(2R), Oy = mg/2 6.0 g G a -R-